The EvCheck class

(PECL ev >= 0.2.0)

Introdução

EvPrepare
and
EvCheck
watchers are usually used in pairs.
EvPrepare
watchers get invoked before the process blocks,
EvCheck
afterwards.

It is not allowed to call
EvLoop::run()
or similar methods or functions that enter the current event loop from
either
EvPrepare
or
EvCheck
watchers. Other loops than the current one are fine, however. The
rationale behind this is that one don't need to check for recursion
in those watchers, i.e. the sequence will always be:
EvPrepare
-> blocking ->
EvCheck
, so having a watcher of each kind they will always be called in pairs
bracketing the blocking call.

The main purpose is to integrate other event mechanisms into
libev
and their use is somewhat advanced. They could be used, for example, to
track variable changes, implement custom watchers, integrate net-snmp or a
coroutine library and lots more. They are also occasionally useful to
cache some data and want to flush it before blocking.

It is recommended to give
EvCheck
watchers highest(
Ev::MAXPRI
) priority, to ensure that they are being run before any other watchers
after the poll (this doesn’t matter for
EvPrepare
watchers).

Also,
EvCheck
watchers should not activate/feed events. While
libev
fully supports this, they might get executed before other
EvCheck
watchers did their job.